Carolina wrens get ready to make nests

If you're an early riser, you've probably heard a distinctive bird song this week. It's a loud, ringing, musical whistle. Often it's a series of triplets -- "Tea kettle! Tea kettle! Tea kettle!" or "Chirpity, chirpity, chirpity!" It's the song of a Carolina wren, and it's a reliable harbinger of spring.
Although most songbirds won't begin nesting for four to six more weeks, Carolina wrens are among the earliest backyard nesters. And because they get a head start on the season, they can raise as many as three broods before the end of the summer.
Carolina wrens are small, handsome birds measuring about 5.5 inches long. They are chestnut above, cinnamon below, and have a prominent white eye stripe. They spend most of their time in dense vegetation, and they are more often heard than seen. But they are common around homes and commonly explore sheds, barns and open garages.
Unusual nesters
In fact, it is the Carolina wren's affinity for nooks and crannies that often brings it to our attention. Although classified as cavity-nesters, Carolina wrens usually forsake tree cavities and nest boxes in favor of more unusual nest sites. Over the years I've found their nests in a mail box, a can of nails, an old boot, a hanging plant, and a clothespin bag. Two years ago they discovered a one-gallon bucket hung from a hook just outside the side door to the garage.
The female Carolina wren usually lays her first egg in mid-March, at least two weeks before I find the first bluebird eggs of the season. The nest is loosely constructed and large enough to fill the selected space. Materials may include twigs, grass, strips of bark, dead leaves, moss, hair, feathers and sometimes even bits of paper, plastic, string and snakeskin.
Typically the nest is domed, with an entrance on the side. Both sexes help build the nest, but the male does most of the work. That seems fair because only the female incubates the four or five eggs for about 14 days. Meanwhile, the male defends the territory, which may range from two to ten acres, and often feeds his mate on the nest.
What do they eat?
Carolina wrens prefer live food and are great to have around the garden. They eat a variety of insects, spiders, caterpillars and egg cases. When I offer mealworms, they gobble them up, and though their decurved bill is adapted for handling live prey, they also help themselves to sunflower kernels and shelled nuts.
I've often been frustrated by the peculiar nest sites Carolina wrens choose, because finding them can be difficult. So at a meeting of the Ohio Bluebird Society a few years ago, I was delighted to discover that Wayne Davis, co-author of Bluebirds and Their Survival (University Press of Kentucky, 1995), had come up with a nest box for Carolina wrens. Davis credits Columbus birder Bob Orthwein with the design, which takes advantage of this wren's loose definition of a cavity.
Easy to make
The Orthwein/Davis Carolina wren box can be made with any type of wood except treated lumber. A 1-by-4 pine board, half-inch exterior plywood, or suitably sized scrap lumber works well. The back can be quarter-inch plywood.
Size is not critical because wrens fill the space available, but the interior dimensions should be no smaller than six inches wide by four inches deep by six inches high. The front is a piece of wood half the height of the sides, so the entrance to the box is the wide slot on the top half of the front.
Davis describes Carolina wren nesting sites as, "back in under," and says, "if you place these boxes under a porch roof, under a deck, or in sheds or outbuildings, Carolina wrens will find them irresistible."
For diagram of the Orthwein/Davis wren box and plans for a simple bluebird/chickadee nest box, send me a self-addressed, stamped, business-size envelope and $2.
Send questions and comments to Dr. Scott Shalaway, R.D. 5, Cameron, W.Va. 26033 or via e-mail to sshalaway@aol.com.